1. Field of the Invention
The invention relates to a method of obtaining a structure on a semiconductor wafer by etching through structures defined by a photoresist mask and then stripping the mask.
2. Description of the Related Art
In semiconductor plasma etching applications, a plasma etcher is usually used to transfer a mask pattern into a circuit and line pattern of a desired thin film and/or filmstack (conductors or dielectric insulators) on a wafer. This is achieved by etching away the films (and filmstacks) underneath the photoresist materials in the opened areas of the mask pattern. This etching reaction may be initiated by the chemically active species and electrically charged particles (ions) generated by exciting an electric discharge in a reactant mixture contained in a vacuum enclosure also referred to as a reactor or process chamber. Additionally, the ions may be also accelerated towards the wafer materials through an electric field created between the gas mixture and the wafer materials, generating a directional removal of the etching materials along the direction of the ion trajectory in a manner referred to as anisotropic etching. At the finish of the etching sequence, the masking materials are removed by stripping them away, leaving in its place a replica of the lateral pattern of the original intended mask patterns. During the etching process, the mask materials are usually eroded and/or damaged in exchange for the pattern transfer. Consequently, some of the damage and erosion also may be transferred to the underlying layers leaving such undesirable pattern distortions such as striation, CD enlargement, faceting, etc.
In addition, for low-k dielectric materials (k<3.0), during the stripping of the photoresist, damage may occur to the low-k dielectric material, which may increase the k value. In such a stripping process, it is desirable to limit such damage during the stripping process.